The new legislation is the first time in a decade that lawmakers from both sides of the aisle have come together to put forth serious climate policy. And like the MARKET CHOICE Act, it uses a fee to reduce pollution across the economy and includes “environmental integrity mechanisms” (EIMs) — provisions that tie a carbon fee to clear, measurable pollution reduction goals and keep us on track to meet those goals. EIMs are still a relatively new concept on the climate policy scene, but leading thinkers have begun to pay them significantly more attention, and it is clear they are emerging as a critical component of any serious carbon fee proposal: and with good reason.

A carbon fee – which sets a price per unit of pollution – prompts the economy to respond by providing powerful incentives to reduce that pollution, but it cannot guarantee the environmental result. While energy and economic modeling tools can provide critical insight into possible or likely outcomes, they cannot provide certainty over the magnitude of the impact. That’s why it is critical to include EIMs designed to provide greater assurances that a fee will deliver on its pollution reduction potential.

Momentum is building for urgent action on climate change. Last week, hundreds of protestors flooded into the Capitol calling for lawmakers to act. The recent Intergovernmental Panel on Climate Change report on the climate impacts of 1.5 degrees of warming and the U.S. National Climate Assessment paint a stark picture: the effects of warming are already here and there is no room for more delay if we are to avert disastrous impacts on human health and our economy. As this demand for action has gotten louder, so has the call for solutions that guarantee the results we need.

There is growing recognition that we need serious solutions to these pressing problems – and that means performance-based policy designed to ensure pollution reductions occur at the pace and scale the science demands. EIMs play the role of an insurance mechanism – they may never be triggered if a fee performs as expected, but provide critical safeguards in case it does not. As Rep. Ted Deutch, the author of the new bill, recognized, a price on pollution can harness the power of the market and provide a flexible cost-effective means of achieving results. But Rep. Deutch and the bill’s co-sponsors also realized that it is no longer acceptable to simply set a price and walk away, hoping the fee does the job. We also need limits on pollution, and effective mechanisms to ensure we meet our critical emissions reduction goals.

Indeed, the most straightforward way to cut pollution is to place enforceable declining limits on pollution, guaranteeing the environmental outcome, while giving businesses flexibility to determine the best way to meet it. We already have proof that those kinds of policies can help meet environmental goals faster and more cheaply than expected while growing the economy.

Regardless of the approach we take, the cornerstones of good policy design are the same: clear and measurable emission reduction goals, effective provisions to ensure they are met, and flexibility in how to meet them coupled with strong incentives to do it cheaply and efficiently. In the context of a carbon fee, that means including an EIM.

Ultimately, in order to achieve the dramatic transformational change needed to reach a 100% clean energy economy and the pollution reductions that science demands: net-zero emissions as soon as possible, a portfolio of policy approaches is needed (as others have pointed out). This means not only a limit and a price on pollution, but also investing in innovation and development of promising emerging clean energy technologies. It also means putting in place other programs that accelerate deployment of clean transportation infrastructure and promote electrification of cars and buildings. And it means encouraging states and cities to continue to lead and take action to cut pollution, pushing beyond federal requirements.

The seeds of future progress in Congress are being planted and demand is growing for durable and effective solutions that ensure environmental goals will be met. The key metric for any climate policy is environmental performance – lawmakers on both sides of the aisle are demonstrating they recognize this fundamental principle.